Starting out in Macrophotography

I've been interested in Macrophography for a while; however, historically, I was limited by equipment. With a Nikon D5300 and a kit lens, I could get good shots of larger insects but not get in very close.

Having explored my options a little, I settled on buying a 70mm F2.8 DG MACRO to go with my Sony Alpha 6600. Unfortunately, the Sigma lens isn't a perfect fit as the DG notation on the lens shows that this is a full-frame lens on an APS-C camera. However, given that I want to replace my Nikon D5300 with a Sony Alpha 7R V when released and move to full-frame high resolution in the future, this lens is future-proofed.

I went out into the back garden and started trying to compose some shots of the Antirhinums and Alliums:

Happy with the two shots (out of about fifty) that came out well, I experimented with picking flowers and bringing them indoors to use with the flash and a backing card:

Learning to use the off-camera flash to create a better fill improved the quality and clarity of the pictures immensely.

I'm happy with the lens, although I think the Sony G Master FE 90mm F2.8 Macro G OSS is a better lens, albeit at twice the price. Manual focus is a must with the Sigma, and I found connecting it to my computer to aid in focusing and previewing images helpful.

I'm proud of my beginnings, plenty of room for improvement - any suggestions on what to shoot next? And how to improve my macro photography?